1. Field of the Invention
The present invention is directed to a method of generating a strip waveguide using a selective etching process whereby the laser active strip is protected from exposure.
2. Description of the Prior Art
A method of the type with which the present invention is concerned for manufacturing a semiconductor laser in the form of a strip laser utilizes a laser-active zone which is buried. The method is usually carried out such that an elevated strip having a width of the strip laser is etched into an epitaxial layercomprising a double hetero-layer structure. In a second epitaxial process, the lateral marginal edges of the strip which often have multiple layers for better current blocking are closed off with indium-phosphorus. For better wetting in the second epitaxial process and for cleaning the lateral marginal surfaces of the strip, a remelt or a dissolution method is known wherein the lateral marginal surfaces are etched back by erosion melting, using less than saturated melts. The dissolution or remelting, however, occurs very briefly, for example, for 2 seconds with an indium-phosphorus melt or with an indium-arsenic melt in order to prevent excessive etching of the laser-active layer of the strip laser. The lateral marginal edges of the strip laser remain essentially planar. After the brief remelting, the erosion melt is discharged and a growth melt for growing a epitaxial layer is subsequently applied to cover the lateral edges of the strip. Between the discharge of the erosion melt and the employment of the growth melt, the lateral surfaces are exposed an subjected to chemicals and/or contaminating atmospheres, for example, the atmosphere of the process reactor. As a result, the quality of the resulting lateral marginal surfaces between the strip and the subsequently grown epitaxial layer is reduced. This reduced quality causes imperfect lateral hetero-junctions which give rise to aging mechanisms characteristic of semiconductor lasers which employ a buried hetero-layer structure with the laser-active zone in a buried location.